This invention relates generally to jars that are used in freeing tools which become stuck in the well bore. More particularly, but not by way of limitation, this invention relates to an improved rotary jar for use in freeing well tools and the like that become stuck while drilling a well bore.
Rotary drilling jars are illustrated in U.S. Pat. No. 1,801,673 issued to G. S. Knox on Apr. 21, 1931, in U.S. Pat. No. 3,834,471 issued Sept. 10, 1974 to Clifford C. Bottoms, and in U.S. Pat. No. 4,511,007 issued Apr. 16, 1985 to Thomas Jung et al. Each of these patents illustrates a different arrangement of a jar that includes a different structural arrangement for locking the relatively moving parts of the jars together until a predetermined tension or compression force is applied thereto. When the predetermined force is exceeded, the relatively moving parts are released, permitting shoulders thereon to come into engagement, causing an impact or jarring action to be transmitted into the drill string in which the jar is located and into any well tool which may be stuck in the well.
An object of this invention is to provide an improved jar for use in a drilling string which reduces wear on component parts, reduces maintenance, increases the rapidity with which the lock releases the relatively moving parts of the jar, and which transmits rotary torque therethrough from the drill string to the drill bit in either direction.
Another object of the invention is to provide an improved jar having the above advantages, and in addition, prevents the application of the drilling string weight to the jar locking mechanism when the drilling string is being lowered into or removed from the well bore.